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Congratulations to PFC member Joshua Frieman!
April 27, 2017
The Division of Astrophysics (DAP), organized in 1970, engages in observational and theoretical investigation that relates to the study of physical processes in stars and other discrete galactic sources, galactic structure and evolution, the early history and evolution of the Universe, and the Sun and solar activity. Division interests also have significant overlap with other APS divisions such as Particles and Fields, Nuclear Physics, and Plasma Physics.
The Halo Boundary of Galaxy Clusters in SDSS
April 24, 2017
recent study, which presents strong evidence for the physical edge of galaxy clusters using public data from the Sloan Digital Sky Survey.
The existence of such physical edges associated with sharp density drops due to the density caustics formed by accreting matter was predicted by KICP researchers Benedikt Diemer and Andrey Kravtsov in 2014, as part of Diemers PhD research. In a follow-up study, Diemer, Kravtsov and a former KICP fellow Surhud More (currently at Institute of Physics of the Universe, Tokyo, Japan) have shown that the-edges can be considered to be natural physical boundary of dark matter halos that provide the gravitational "back-bone" for the structures observed in the galaxy distribution.
In the recent study, co-led by Chihway Chang and Eric Baxter - a former KICP student and currently a postdoctoral fellow at the University of Pennsylvania - the density drop associated with the halo edges was detected in the galaxy distribution around cluster centers.
Cosmological simulations show that massive galaxy clusters we see today have been accreting galaxies into their deep gravitational potential over the cosmic time. The process of galaxies "falling into" the cluster's potential well is a fairly clean and universal process that depends only on basic quantities of the cluster such as mass and accretion rate. One of the result of this simple picture is a sharp feature in the number density of galaxies around clusters - an imprint of the caustic formed by the infalling galaxies as they reach the first apocenter of their orbit, or the "edge" of the galaxy cluster. Researchers called the distance of the edge the "splashback" radius, as galaxies literally "splashing back" to that radius after they accrete onto cluster.
Together with collaborators in UPenn and UIUC, that included KICP faculty Andrey Kravtsov, Chihway Chang and Eric Baxter, examined distribution of galaxies around a sample of clusters identified within the SDSS. The existence of the edge in the galaxy distribution within clusters was confirmed. In addition, the analysis revealed that properties of galaxies around cluster are sensitive to existence of the edge. Outside the splashback radius, the mix of red and blue galaxies was approximately independent of the distance from the cluster center, while inside the splashback radius the mix is abruptly changes towards a larger fraction of red galaxies. This indicates that the edge is a real dynamical feature and that majority of galaxies get transformed by the cluster environment from blue to red in less than one orbital period.
This figure shows the fraction of red and blue galaxies around galaxy clusters. The sharp change in the red fraction indicates that galaxy tend to turn red once they enter the edge of the cluster, which is marked by the grey vertical band. (Figure modified from the paper "The Halo Boundary of Galaxy Clusters in the SDSS".)
Related KICP references:
The Event Horizon Telescope's historic quest
April 13, 2017
The PFC will welcome 5 new Fellows in the Autumn of 2017
March 9, 2017
Macarena Lagos will receive her PhD from Imperial College London. Her research focuses on theoretical cosmology, specifically on analysing the viability of alternative gravity theories and developing methods to test gravity at large scales. At KICP, Macarena hopes to continue her current research and start new collaborations with its members.
Kirit Karkare will join us as a joint Grainger and KICP Fellow after completing his degree at Harvard University, where he worked on hardware and systematics analysis for the BICEP/Keck CMB polarization experiments. At the KICP, he plans to continue working on the CMB with BICEP and SPT, and on detector development for line intensity mapping and measurements of high-redshift galaxies.
Wai Ling (Kimmy) Wu did her graduate work at Stanford University with the BICEP/Keck team on the design, testing, and deployment of BICEP3 -- a small aperture CMB polarimeter that aims to target the inflationary gravitational wave B-mode signature. She then moved to UC Berkeley to work with the SPT team on the SPT-3G receiver and on delensing CMB B-mode maps, an important step to further constraint the inflationary B-mode signature. At KICP, she plans on extending her delensing work with BICEP/Keck and SPT datasets and looks forward to exploring new avenues to understand the cosmos with fellow KICP researchers.
Grayson Rich carried out research at Triangle Universities Nuclear Laboratory (TUNL) while a graduate student at the University of North Carolina. As a part of the COHERENT Collaboration, he has been working towards the first observation of coherent, elastic neutrino-nucleus scattering (CEvNS): a low-energy neutrino-nucleus interaction arising from the standard model but still undetected over 40 years after its prediction. As a KICP Fellow and an Enrico Fermi Fellow at the Enrico Fermi Institute, he will maintain involvement with COHERENT and continue to advance an effort he spearheaded at TUNL to provide definitive characterizations of the responses of neutrino and dark matter detector systems, working with several groups at KICP and the broader astroparticle physics community. He also hopes to work with KICP and EFI members to exploit high-energy astrophysical signals, seeking insight into cosmological questions and the properties of fundamental particles.
Hsin-Yu Chen has been selected for a Cronin Fellowship
February 15, 2017
Angela V. Olinto,
Homer J. Livingston Professor and Chair Department of Astronomy & Astrophysics
Deflategate: Cold Wet Footballs, Ideal Gas Laws and Accusations of Cheating
February 8, 2017
Twenty-eight (28) high school students in KICP's Space Explorers program put these arguments to the test. Over the course of two weeks, students critically evaluated over a dozen arguments made by both sides, ranging from court documents, to college lectures, to tweets. Despite the strong opinions, contradictory claims, and often factually incorrect information found in these arguments, the Space Explorers managed to identify the critical questions that needed to be resolved to determine if Deflategate could be caused by purely innocuous physics and designed an experiment to address them. Their experiment revolved around measuring the effect that wetness had on the rate at which cold footballs warm up and increase in pressure.
To date their results are inconclusive. One trial found nothing suspicious about the pressure drop, and a second could not explain the low pressures in the Patriots' footballs. The Space Explorers themselves are split down the middle about how to interpret their results and will debate the best way to resolve this difference at the pre-Super Bowl Saturday class.
Summer Undergraduate Researcher Michael Foley Wins AAS Chambliss Student Medal
February 1, 2017
Former PFC Fellow Eric Dahl honored with a PECASE
January 24, 2017
On MLK Day King College Prep Cosmology Club Explores Dark Matter
January 16, 2017
Space Explorer Naa Ashitey is the Quest Bridge Finalist for the University of Chicago
December 12, 2016
QuestBridge is a nonprofit program designed to assist high-achieving, academically motivated students from low-income backgrounds apply to top colleges around the nation. The program features the National College Match, in which students rank and apply to up to eight of QuestBridge's partner colleges. Students who are matched receive a generous four-year, no-loan scholarship.
Mark SubbaRao to become IPS President-Elect
December 7, 2016
Mark SubbaRao won the recent International Planetarium Society (IPS) election and will assume the role of President-Elect of this prestigious society at the beginning of 2017. In two year's time he will become the President of the IPS for a two year term.
In his candidate's statement, Mark said "I am running for IPS President to help shape the future of the planetarium, this wonderful medium which can inspire the public like nothing else.
... If elected, I will focus on building a more active organization and expanding professional development opportunities. We will support research that demonstrates how effective the planetarium is."
Read the entire statement at the International Planetarium Society website.Learn more >>
Chicago high school students visit to experience "A day in the life of a scientist"
November 15, 2016
As part of her activities, Professor Freedman recently arranged for students to visit the Eckhardt Research Center for a discussion and tour of the KICP and Astronomy & Astrophysics labs and the Pritzker Nanofabrication Facility. Students visited the PNF and the KICP labs of Professor Erik Shirokoff (where Associate Fellow Peter Barry described the lab equipment and activities), and gathered in Professor Stephan Meyer's lab to see a camera that will be used in a balloon-borne experiment to detect cosmic ray showers. Professors Meyer and Freedman also spoke to students about various aspects of their research and their lives as scientists.
Professor Meyer explains Extensive Air Showers to the visiting students.
Stephan Meyer showing the visitors around his lab.
Associate Fellow Peter Barry explaining a piece of apparatus in the Shirokoff lab.
SPT-3G Camera Has Shipped to the South Pole
November 1, 2016
"SPT-3G: A Next-Generation Cosmic Microwave Background Polarization Experiment on the South Pole Telescope".
Congratulations to Matthew Richardson, PFC Fisk-Vanderbilt Bridge Program participant!
October 10, 2016
"Through a careful analysis of data collected by the MIDAS detector installed at the Pierre Auger Observatory, Matt has established the best limits on microwave emission from Extensive Air Showers induced in the atmosphere by Ultra-High Energy Cosmic Rays (UHECR). His results, an improvement by more than one order of magnitude over previously published limits, place strong constraints on the prospects of this technique for UHECR detection."
- Paolo Privitera
Matt has received a position of Postdoctoral Research Scientist at the Planetary Science Institute.
"Bruce Winstein", biographical memoir by Mel Sochet and Michael Turner
September 27, 2016
Learn more >>
2016 Yerkes Summer Institute: Spy vs. Spy
August 16, 2016
The 2016 Yerkes Summer Institute (YSI) was filled with secrecy, deception, and espionage. At YSI, high school students in the Space Explorers program played the role of 20th-Century spies to handle secret information: revealing, concealing and distorting information. Through three day-long lab activities, the students explored connections between spying and science. In the "Secret Photos" lab, they studied angular size, resolution, and the film-development process in order to effectively gather information on "enemy operatives" using 35 mm cameras. In the "Radio Beams" lab, students designed, built, and tested a system to transmit audio via an amplitude-modulated (AM) laser, which allowed them to secretly communicate across long distances. Lastly, techniques to securely communicate were examined in the "Codes and Ciphers" lab, which also served as an introduction to modern cryptography. After cycling through these three day labs, the students broke into three new groups and took one of the labs a step further: one group doctored photographs to spread false information, another built AM radio transmitters and receivers, and the last created treasure hunts using codes and ciphers for the clues. Nighttime activities included: observations with the Yerkes telescopes, astrophotography, explorations of the constellations which focused on what current research can tell us about them (e.g. most know exoplanets were found by Kepler in the constellation Cygnus); and bad weather activities that included examinations of the veracity of viral internet photos, and stories of famous spies. The week's spy-themed activities not only introduced the students to the importance of privacy in the digital age, but also to the concepts and skills that are integral to any modern STEM career.
Congratulations to Dr. Sean Johnson!
July 18, 2016
"Studies of the relationship between galaxies and the inter/circum-galactic medium".
"Sean's thesis work casts new light on the intricate physical processes that drive the baryon cycles between star-forming regions and the intergalactic space. He led an ambitious survey of the galactic environments around chemically-enriched gas revealed in strong absorption against a background source. Sean's thesis sample represents the first of its kind in terms of both the scale and depth of galaxy survey data in quasar fields. It provides a pathfinder for future large-scale studies that will combine wide-field galaxy surveys with absorption spectroscopy to advance our understanding of chemical enrichment in low-density regions away from galaxies."
- Hsiao-Wen Chen, PhD advisor
Sean will be starting as a Carnegie-Princeton/Hubble fellow at Princeton in the fall.
Congratulations to Dr. Asher Berlin!
July 8, 2016
"Phenomenology of Particle Dark Matter".
"Asher's work has covered a broad range of topics related to dark matter and efforts to reveal its particle nature. He has worked on theory calculations relevant to underground and space-based dark matter searches and to searches for dark matter at the Large Hadron Collider. More recently, he has worked on non-standard ways in which dark matter may be have created in the early universe."
- Dan Hooper, PhD advisor
Asher has received a Post Doctoral Fellow position at SLAC.
Congratulations to Dr. Brittany Kamai!
June 22, 2016
"Hunting for MHz Gravitational Waves with the Fermilab Holometer".
"Brittany's thesis uses the Holometer data for a unique measurement of gravitational waves in the Megahertz frequency band. Her analysis sets limits on possible exotic sources of gravitational waves, such as black holes in binaries of very small mass -- radiating at frequencies ten thousand time higher than those recently measured by LIGO."
- Craig J. Hogan
Brittany has received a position of LIGO Instrumentation Postdoctoral Fellow at the California Institute of Technology.
Dan Scolnic Competes in Famelab national finals
May 18, 2016
FameLab USA is a NASA-sponsored, science-based take on American Idol, aimed at fostering an open community for science communication and development.Learn more >>
Wayne Hu elected to the National Academy of Sciences
May 3, 2016
News from the National Academy of Sciences
Wayne Hu is a senior member of the KICP and the Horace B. Horton Professor in the Department of Astronomy & Astrophysics, Enrico Fermi Institute, and the College. His research focuses on the theory and phenomenology of structure formation in the Universe as revealed in Cosmic Microwave Background anisotropies, gravitational lensing, galaxy clustering and galaxy clusters.